*{
    box-sizing: border-box;
}
main{
    margin: 10px auto;
    width: 602px;
    border:1px solid black;
}
main header{
    background-color: black;
    line-height: 40px;
    height: 40px;
}
header span{
    float: left;
    width:200px; 
    color: white;
    text-align: center;
    border-right: 1px solid gray;
}
ul{
    display: none;
}
ul:nth-of-type(1){
    display: block;
}
.current{
    background-color: gray;
}